When Posting Is Believing

Abstract. Social network sites (SNS) facilitate the expression of users’ opinions to a large audience. This research aimed to investigate whether the characteristics of this new media context strengthen the adaptation of opinions to the majority and lead to an internalization of the expressed views. Based on literature on public self-presentation and identity shifts, it was assumed that the publicness of and the identifiability within SNS elicit stronger expression effects than online forums or non-public settings. A between-subjects experiment ( N = 302) varied the visible majority opinion on a news issue as well as the media context in which participants were asked to write down their opinion. Results showed significant adaptation effects to the majority (positive vs. negative comments) across media contexts. The internalization of attitudes was stronger in SNS groups with a more relevant audience but also occurred in other settings. Consequences for the formation of public opinion are discussed.